Passat running cold

cantdecide

For those who remember my recent threads on my car search, in the end, I got a 123k ‘02 T(red)DI Passat as a trade car from a salesman mate. I had it checked over and there wasn’t too much wrong with it for the money. TB just done. The usually ball joints, CV boots and that kind of thing but tbh, I noticed that the temp needle had a slight tendency to float, if not on the 90 mark, just below it. I collected it on Monday and intended on giving it a couple of weeks and getting it serviced and repaired.

However, yesterday, on the 6 mile trip to work it failed to heat up. On the way home, it did the same. At home, I popped the bonnet and found that the expansion bottle to be full etc but the coolant was tepid. I then had a small journey to make about half an hour later and after half a mile, the temp needle went from the bottom to 90 in 10 or 15 seconds. It then stayed hot albeit with its usual tendency to hover just below the 90 mark. This morning on the way to work, it failed to heat up again.

Does this sound like something that needs urgent attention??

BlackWizard

THe ECU uses this sensor to adjust the fuel/air mixture. So has your MPG dropped much?

It may be a faulty coolant sensor. I've no idea if that will cost alot to replace. I've no idea where it is in the VW TDi engine.

trad

VW's temperature guages are fickle. I had a Caravelle and the temperature gyage worked when it felt like it. I googled it before and someone had posted a repair to the circuit board on the clocks, poor soldering if I remember correctly.

THe chances are your engine is running fine but its just the clocks. I've often seen new/old vw clocks for sale on ebay, might be worth a look.

remotesensor

I had the same problem with the same engine last week. Cost me 40 quid to replace the sensor and get an overall check but that's only an initial step because it could be something else that's wrong. The job was only done last week and the gauge seems to be behaving normally now but I'm still keeping an eye on it.

Heroditas

Speaking of cars running cold, I had my timing belt and water pump changed on my A4 1.8T a while ago and the temperature gauge seems to be running at 75C rather than 90C like it had been previously.

Apart from that, it seems to be running fine and the fuel consumption is better than ever.
Should I be worried? I was under the impression the engine temperature should be reading 90c when running for longish periods

cantdecide

BlackWizard wrote: »

THe ECU uses this sensor to adjust the fuel/air mixture. So has your MPG dropped much?

It may be a faulty coolant sensor. I've no idea if that will cost alot to replace. I've no idea where it is in the VW TDi engine.

I've only done about 100 miles in the car since I picked it up so it's hard to say. I would have thought that the temp sensor would be independent of the thermostat/ plumbing etc? Would it explain cool water in the system??

DublinDilbert

cantdecide wrote: »

I've only done about 100 miles in the car since I picked it up so it's hard to say. I would have thought that the temp sensor would be independent of the thermostat/ plumbing etc? Would it explain cool water in the system??

Does she come up to temperature in traffic? Then drop off when you hit the open road? Does the internal heater work? If it does this it sounds like the thermostat has failed open or slightly open.....

Generally the internal heater tells you more about what's happening in your cooling system than anything else...

alo1587

VW coolant temperature sensors give a lot of trouble after time.Does the air from the heater in the car feel warm? Has the thermostat been taken out of the engine,or is it still there do you know